1. Field of the Invention
The present invention relates to a light modulating unit and an image projection apparatus using the light modulating unit.
2. Description of the Related Art
With the recent increase in the resolution of imaging devices, there has also been a growing demand for an increase in the resolution of image projection apparatuses that display images taken. Accordingly, much effort has been made to develop display devices (light modulating devices) with a large number of pixels. However, the display device does not have a sufficient resolution compared to the imaging device. The light modulating device is sometimes called a spatial modulation device.
A proposal described below has been made as a technique to realize a high resolution using a light modulating device (LCD or the like) with a limited number of pixels.
Jpn. Pat. Appln. KOKAI Publication No. 10-304284 and Jpn. Pat. Appln. KOKOKU Publication No. 7-52262 propose a technique to realize a high resolution using two light modulating devices (LCDs) and a polarization beam splitter (PBS). The two light modulating devices are arranged so that their images are offset from each other by half a pixel pitch. The light modulating devices are also configured so that their directions of polarization cross at right angles. The resolution is increased by using the PBS to synthesize a P-polarized light image and an S-polarized light image generated by the two light modulating devices.
However, this proposal simply synthesizes the images generated by the two light modulating devices, using the PBS. Because of its nature, the PBS can synthesize only two images, a P-polarized light image and an S-polarized light image. This technique can thus realize only two-point pixel shifts. That is, this proposal cannot realize three-or-more-point pixel shifts. Therefore, with this proposal, it is difficult to sufficiently increase the resolution.
Jpn. Pat. Appln. KOKAI Publication No. 2002-268014 proposes that a two- or four-point pixel shift be realized by using one light modulating device and supplying an image from the light modulating device to a beam shifting section (wobbling unit) through a PBS. However, if a four-point pixel shift is carried out, four points are temporally sequentially shifted, so that a light intensity per pixel is one-fourth of a normal value. It is thus difficult obtain a sufficient light intensity. Further, since the four points are temporally sequentially shifted, a time lag may occur, resulting in a flickering image.
Thus, disadvantageously, with the conventionally proposed techniques to increase the resolution, it is difficult to sufficiently increase the resolution, to obtain a sufficient light intensity, and to obtain images free from flickering. Accordingly, it has been difficult to increase the resolution and to obtain images with an excellent display quality.
It is an object of the present invention to provide a light modulating unit and an image projection apparatus that enable the resolution and display quality to be improved.